1. Field of the Invention
The present invention relates to a method for gas stunning of poultry for slaughter and of the kind stated in the preamble of claim 1.
2. Description of the Prior Art
Over time, many different methods have been proposed for gas stunning of poultry for slaughter arriving at the poultry slaughterhouse in transport crates, with no remarkable success. In practice however, several parameters must be considered in order to be able to optimize a method for gas stunning of poultry for slaughter.
To optimize the method, the following parameters must be considered:                Conveying speed (capacity of the system)        Size and number of birds in the transport crates.        The physical condition of the poultry flock which is determined by continuously observing variations in a stress condition or resistance of the poultry that are significant for determining the time necessary for stunning the poultry which further may vary because of conditions in broiler houses, temperatures, transport time, and waiting time in the slaughterhouse.        
To optimize the gas stunning it is furthermore necessary to be able to continuously consider all these parameters prior to and during gas stunning of the poultry supplies delivered to the slaughterhouse, and continuously apply the most advantageous parameters to achieve optimum gas stunning of the actual chicken flock at any time to be stunned and slaughtered, respectively.
To optimize these parameters, different periods of stunning time can be used, but variations in the gas concentration, and variations of gas concentration in the different sections of the conveying route must also be taken into account, depending on the transport route length and transport route location in the stunning chamber.
The gas concentration may be monitored and controlled by means of sensors having different locations, and a PLC control system. Adjustment of the stunning time and concurrent variation of the gas concentration requires a change in the previously used methods by which a given slaughtering capacity of number of birds per minute required a fixed conveying time through stunning chamber. A given rate of slaughtering slaughtering capacity will always be determined by other subsequent parameters that cannot be changed immediately. Consequently it may furthermore be necessary to be able to change the degree of stunning, depending on the condition of the poultry upon arrival at the slaughterhouse and unloading for slaughter.